The purpose of the proposed research is to examine pigeons' choices under laboratory conditions that arrange food at the same unit price, defined as a cost-benefit ratio of work requirements and reward magnitude. Some empirical research has found equal reward consumption under conditions arranging equal unit prices, irrespective of the size of cost-benefit components. These findings have led to predictions of indifference (i.e., equal preference) when such conditions are arranged in a choice context. Previous research, however, has found systematic deviations from indifference when cost and benefit components differ. A primary aim of this research program is to gain a better understanding of the determinants of such deviations, exploring the predictions of a modified version of the unit price model that includes work requirements and delay as separate cost factors. These experiments will provide additional information in an area wherein no comparable data exist, and will help to integrate choice research from psychology and economics. This research may also reveal processes useful for understanding human behavior in situations involving health and safety behavior.